Process for producing paraffinic hydrocarbons



ture of parafllnic portions of olefins.

Patented June 16,1942

PROCESS FOR PRODUCING P HYDBOOARBONS William E.

Union Oil geles, Calif.,

Glaims.

relates to the manufachydrocarbons of a branched chain structure particularly suitable for use as fuel in automobile and aviation engines. More specifically, the invention includes a process for combining certain isoparafilnic hydrocarbons with olefinic hydrocarbons to produce branched chain parafflnic hydrocarbons,'these products of reaction being particularly suitable as a motor fuel, or as a constituent thereof, because of their high anti-detonating or slow burning characteristics. The invention further includes the use of special catalyst mixtures and of condition of operation for the manufacture or synthesis ,of the described valuable compounds.

The adoption of high compression ratios for automobile and aviation engines has caused the petroleum industry to resort to the use of cracking operations as a general means of producing motor fuels having high anti-knock values. However, cracking operations produce undesirably large losses, for example in the form of gases which usually contain considerable pro- Aside from these oleiinic hydrocarbons of the normally gaseous and of the normally liquid types are also obtained from other sources. Thus, oleflns occur along with paraflinic and other saturated hydrocarbons produced by gas-making processes, as well as byproducts from various chemical industries.

The present invention .Also, oleflnic hydrocarbons are obtained by a simple dehydrogenation paraflinic hydrocarbons.

In general, oleflnic hydrocarbons are relatively more chemically active than other classes of hydrocarbons. Thus, even under comparatively mild catalytic influences, the olefinic hydrocarbons exhibit a high reactivity in their tendency to polymerize and to form substances of higher molecular weight. On the other hand, paramnic hydrocarbons, for example isobutane, isopentane, etc., normally occurring in natural gas or any similar or related hydrocarbon fractions are usuof the corresponding ally considered to be more orless chemically inactive.

In one of its embodiments, the present process is directed to'the' efllcient utilization of the above described isoparaflinic and oleflnic hydro- -carbons, and particularly the lower molecular weight or normally. gaseous fractions thereof, such as those present in commercial gas mixtures, to produce high antilmock hydrocarbon fractions suitable for use as motor fuels. In another embodiment, the process includes the utilization ofcertain normally liquid oleiinic hy- Bradley, Los Angeles, Korpi, Palos Verdes Estates,

Company of California,

a corporation of California No Drawing. Application SerlaiNo. 208,0

and Karl J. Calm, aasignors to Los An- May 14. less. 58

drocarbons and of scribed more fully hereinbe'low to produce motor fuels or constituents thereof having high anti-detonating characteristics and which are substantially free from products of polymerization. The process described herein is applicable to individual oleiins and isoparafilns, and to their mixtures.

It has been previously discovered that certain isoparafiinic hydrocarbons, and particularly the relatively low boiling or low molecular weight isoparamnic hydrocarbons, may be caused to react with olefinic hydrocarbons to form valuable derivatives thereof. This type of reaction consists in the joining of one or more olefin molecules with one molecule of an isoparaflinic hydrocarbon to produce an alkylated or branched chain parafinic molecule. The product of this reaction is termed an "alkymer to distinguish it from a "polymer" which is the product resulting from the union of two or more olefin molecules. Theoretically, the reaction of an isoparamn with an olefin in the presence of a suitable alkylating catalyst is of a simple character. Thus, the reaction which takes placewhen isobutane is chemically combined with a 'butene in the presence of sulfuric acid may be isobutane butene octane The above equation shows the union of one molecule of isobutane with one molecule of a butene to produce one molecule of an octane. Similar reaction equations may be written for the alkylation of the above or other isoparafllns with various oleiins. As will be brought out more fully hereinbelow the term alkylation" includes not only the simple chemical combination of an isoparafllnic molecule with an olefinic molecule introduced into the sphere of reaction but also the production of branched chain parafllnic hydrocarbons having a molecular weight less than obtained by this simple chemical addition of an isoparafllnic molecule to an olefinic molecule introduced into the reaction sphere.

Olefins, as stated above, when subjected to tact with a sulfuric acid catalyst the reaction parailinic hydrocarbons dethereof.

It is therefore the main object of the present invention to provide a process wherein alkyla- .tion of the isoparanins shall be favored in preference to the polymerization of the olefins introduced into the reaction zone for the purpose' of combining with the isopar'afllnic hydrocarbons. It is a further object of theipresent invention to provide a process wherein valuable motor fuel fractions having high anti-detonating characteristics and substantially free of prodnets of polymerization may be produced by alkylating the low boiling isoparafllnic hydrocarbons with normally gaseous or normally liquid olefins or with both types of olefins. It is a further object of the invention to modify the acid catalyst employed insuch a manner that said modified catalyst will in effect tend to hinder polymerization promote the combining of said olefins with the isoparaflinic hydrocarbons to form the alky'mers It has now been discovered that of the olefins and simultaneously the above and other objects of the present invention may be realized by causing the reaction between isoparafllns and oleflnichydrocarbons to take place in the presence of asulfuric acid catalyst containing a modifying agent which favors the alkylation of the isoparaflins in prefernceto the polymerization of the olefins introduced into the reaction zone. It has been further discovered that the mono-carboxylic and the di-carboxylic acids of relatively low molecular weights, such as acetic acid, propionic acid, butyric acid, oxalic acid, maleic acid, and 'other similar compounds, or mixtures thereof, are highly suitable as such addition compounds or'modifying agents in that when combined with an acidic catalyst of the type of sulfuric acid, the substances or mixtures thereof tend to promote the combining of the olefins with the isoparafilns to produce alkylated isoparaiiinic hydrocarbons, this reaction being favored in preference to the polymerization of the olefins.

The-term isoparamns" or "isoparafllnic hydrocarbons, as employed in the present specification and claims, relates to the lower members, namely,

isobutane, isopentane and isohexane. It has been discovered that the rates of alkylation of these isoparafflnic hydrocarbons, maintaining other conditions equal, are not the same. Thus,

the rate of alkymer formation when isopentane is employed is considerably slower than the rate of alkylation of isobutane, while the alkylation rate of isohexane is even still lower.

As to the terms olefins and oleflnic hydrocarbons, as used herein; they relate to both they normally gaseous olefins, which comprise the hydrocarbons between about propylene and pentenes, and the normallyliquid olefins. such as the hexenes and the higher olefins. It is to be noted, however, that it is not desirable to employ very high boiling olefins since the alkylation reactions become unfavorable when such olefins are employed, It has been found that, when normally liquid olefins are to be employed, it is preferable, although not absolutely essential, to use -75 fractions having not more than about twelve carbon atoms per molecule.

It is to be understood that the reference to isoparafnnic and olefinic hydrocarbons includes the use of these hydrocarbons individually, or in mixtures with other hydrocarbons of the particular class, as well asmixtures thereof with other hydrocarbons.

The invention may be stated to reside broadly in reacting isoparainns of the type of isobutane, isopentane and isohexane, with the described olefinic hydrocarbons in the presence of a sulfuric acid catalyst containing a modifying agent adapted to'favor the alkylation of the isoparafllns in preference to the polymerization of the olefins introduced into the reaction zone. The invention further resides-in reacting the described isoparamnic hydrocarbons with normally gaseousor normally liquid olefins, at optimum temperatures and pressures, in the presence of a sulfuric acid catalyst containing a reaction modifying agent comprising the relatively low molecular weight monoand-di-carboxylic acids, such as acetic, propionic, butyric, oxalic and maleic acids, whereby the poLvmerization of the olefins is in effect hindered and the products of reaction comprise branched chain parafnnic hydrocarbons boiling within the gasoline range, having high anti-detonating characteristics, and being substantially free from polymers within said range.

In a more specific sense, the invention resides in the treatment of the described isoparamns with normallygaseous olefins, between propylene and pentenes, at optimum temperatures and pressures, in the presence of sulfuric acid and a reaction modifying agent of the type of the relatively low molecular weight monocarboxylic and di-carboxylic acids, thereby producing high yields of branched chain saturated hydrocarbons boiling within the gasoline range, having high antidetonating characteristics, and which fractions are substantially free from polymers boiling within this gasoline range. I

The invention also resides in reacting isoparanlnic hydrocarbons having less than seven carbon atoms per molecule with normally liquid olefins preferably below dodecenes, in the presence of sulfuric acid and the above described reaction modifying agent, whereby the products of reaction comprise,branched chain paraflinic hydrocarbons boiling within the gasoline range, having high anti-detonating characteristics and being substantially free from products of polymerization boiling within the gasoline range,

The exact role of the catalyst mixture is not known at the present time. However, it is believed that. the following theory may serve to explain the advantages realized when the aforementioned modifying agent is used in connection with the sulfuric acid catalyst to promote the alkylation of the isoparafllns. It is well known, as stated above. that the olefinic hydrocarbons are highly reactive and are readily poly- 'merized when brought into contact with sulfuric acid, particularly when there is any degree of concentration of the olefins at any point of contact with the sulfuric acid. It is now believed that the'p'resence of the modifying agent of the type of the lower molecular weight mono-carboxylic and di-carboxylic acids, prevents this nce of the sull 85% isobutane and 15% In the meantime, however, the agitation of the mixture has caused the distribution or dispersion of the esters, thus increasing the chance of bringing the olefin molecules into contact with the isoparafiin molecules. Theinitial reaction of the above monoor di-carboxylic acids with the olefins and the subsequent liberation of the olefins (after dispersion in the acid iso-parafiin mixture) is believed to decrease the tendency of polymerization of the olefins.

In one of its preferable embodiments the in-- vention includes the realization of the alkylating reaction substantially in the liquid phase. In this case it is tially a concentration of isoparaflins in excess of the quantity theoretically necessary to combine with the. olefins. For this purpose, the olefins, such as isobutane, isopentane, or is hexane or mixtures thereof, may first be commingled with the catalyst containing the described reaction modifying agent and the olefins may then be gradually introduced into this mixture. Thereaction may be realized at ordinary or room temperatures, such as 70 to 80 F., it being understood that under certain conditions it maybe advisable to conduct the reaction at higher or lower temperatures. The pressures employed are such as will cause the reacting hydrocarbons to be substantially in the liquid state. The mixture of isoparafiins and the alkylating catalyst should be preferably maintained in a state of vigorous agitation.

The presence ofv an' excess of isoparafiiris and the relatively gradual addition of the olefins prevents any local concentration of the olefins which would otherwise favor polymerization instead of the alkylation of the isoparaifins. In other words, the constant presence of an excess of isoparafiinic molecules increases the chances of the contact of an activated olefin with an activated isoparafiin molecule. Simultaneously, the relatively slow addition of the olefins decreases their concentration, thus also increasing the possibility of the alkylation reaction to take place in preference to the polymerization of the olefins.

The following examples are presented for thepurpose of illustrating the advantages obtainable when using catalysts of the type described herein. In these experiments the isoparaifinic iractionemployed comprised a narrow cut obtained from the stabilization of natural gasoline. This fraction consisted of substantially pure butanes in the proportion of approximately normal butane. Obviously, the isoparafiinic fraction to be alkylated according to the present invention may consist of hydrocarbons other than the isobutane, such as isopentane, or may comprise a mixture conta'ining these and other isoparaflins;

The specific olefin-containing fraction employed in the experiments was derived from cracking operations and had substantially the following composition:

preferable to maintain substanvolume of the olefins added, was

Percentage by volume It-is thus seen that this olefin-containing fraction consisted of about 49% of unsaturates above ethylene, the ratio of propylene to the butylene being about 1 to 1. i

In' one of the runs, the a mixture containing 10% acetic acid and 90% catalyst consisted of by volume of glacial by volume of 92.3% H2804. The reaction, which continued for about nine hours. was realized by first commingling 1000 milliliters of the above catalyst with 3300 milliliters of the 85% isobutane containing fraction. The reaction temperature was maintained at 70 F., the pressure being sumcient to maintain the hydrocarbons substantially in a liquid state. Approximately 3800 milliliters of the olefin-containing fraction was then gradually and uniformly conveyed into the reaction zone. The yield of products of reaction .based on the percentage by 126.3%. This fraction contained only 1.3% by weight of olefin polymers. The'overhead fraction, distilled to an end point of 307 F. and comprising 103.6% by volume based on the olefins used, had a knockrating of 89 and an olefin content of only 0.53%.

A second experiment was conducted under substantially the same conditions as those described hereinabove with the exception of employing a sulfuric acid catalyst of a strength of 94.0%, this catalyst being used without the addition of any modifying agent of the class described hereinabove. The useof the slightly stronger acid should have favored the production of alkymers. However, the yield of products of reaction was 102% by volume based on the olefins employed,

this fraction containing 14.5% of olefins. Simirelatively low molecular weight normally gaseous olefins to the specified isoparaflins. it was discovered that in reacting the isoparafilns with normally liquid olefinic hydrocarbons the reaction product comprised a large proportion of saturated hydrocarbons of a branched chain structure boiling substantialy within the gaso- In addition line range. Such hydrocarbons evidently could be formed by an initial scission of at least one of the original reacting hydrocarbons into two or more hydrocarbons of lower molecular weight, and the subsequent reaction of these lower molecular weight hydrocarbons to produce isopar afiinic molecules. simple addition of the introduced olefinic molecules to the isoparaflinic molecules followed by scission of the product. Specifically, this alkylation reaction might be termed cracking alkylation in order to distinguish it from the straight or simple addition of an olefin to an isoparaflin, as already described hereinabove. The cracking alkylation reaction, therefore, may be described as including the step of reacting olefin molecules with isoparaflin molecules to produce one or more paraflinic alkymers which have molecular weights of less than that which would be obtained providing the reaction were one of simple addition in which one olefinic. molecule reacts with one Or, this may be the result of i 4 Q a isoparaflinic molecule to produce a branched chain saturated molecule having a molecular weight equal to the sum of the molecular weights of the reacting olefin and isoparaflin.

Therefore, it has also been discovered that the reaction between the isoparafllns and certain of the olefins (and particularly the normally liquid olefins) in the presence of the described catalyst comprising sulfuric acid and a reaction modifying agent of the class described hereinabove, may result in both the simple alkylation of the isoparaffins by the oleflns added, and. in the cracking alkylation in which, as stated; alkymers are produced which have a lowermolecular weight than would be obtained by simple addition of an isoparafiin to an olefin. The higher molecular weight olefins, as oleflns above dodecenes, however, appear to be unsuitable to react effectively with the isoparafllns to form alkymers, th product of reaction, when using these high molecular weight olefins, containing excessive percentages of polymers boiling above the gasoline range.

The term gasoline boiling range," as employed herein, refers to the average boiling range of fuels used in ordinary automobile engines. Generally speaking, such a gasoline has an initial boiling point of about 100 F., and a maximum or end point of around 425 F. The term "atmospheric pressure refers to pressures in the neighborhood of that extracted by a column of mercury I60 mm. in height while atmospheric temperature and room temperature" relate to temperatures in the vicinity of 70 F. to 80 F.

In carrying out the invention the apparatus used and the conditions of operation chosen in respect to temperature, pressure, proportions of reacting constituents, choice of acid and of the modifying or solubilizing agents, etc., will be varied to suit the individual case. Thus, although the alkylation reactions described herein were i realized at substantially room temperatures, un-

der certain conditions lower or higher tempera tures may be employed.

The quantity of the modifying agent as well as the concentration of the sulfuric acid catalyst may be increased or decreased with 9. corresponding decrease in the quantity or ratio of the acid necessary to promote the alkylation operation. The ratio of the modifying agent to the sulfuric acid may vary from a very small quantity of the modifying agent up to as much as equal parts of the modifying agent and of the sulfuric acid.

It has been found, however, that relatively smallquantities of the modifying agent, such as acetic acid, is suilicient to aid alkylation in preference to the polymerization of the olefins, these mixtures containing up to 15% by volume of acetic acid and the balance sulfuric acid gave excellent results as is indicated by the previous presented examples. i

The above disclosure is merely illustrative of the preferred embodiments of the present invention, andis not to be taken as lmiiting, since many variations thereof may be made within the scope of the following claims without departing from the spirit of the invention.

We claim:

l. A process of forming alkylated parafilnic hydrocarbons which comprises interacting isoparaffinic hydrocarbons'having' less than seven carbon atoms per molecule with oleflnic hydrocarbons,

having more than two carbon atoms per molecule in the presence of strong sulfuric acid and a low molecular weight carboxylic acid.

2. A process of forming alkylated parafllnic hydrocarbons which comprises interacting isoparaffinic hydrocarbons having less than seven carbon atoms per molecule with oleflnic hydrocarbons having more than two carbon atoms per molecule in the presence of strong sulphuric acid and a low molecular weight, di-carboxylic acid reaction modifying agent, wherein the alkylation of the isoparaffins is promoted.

3. In a process of forming motor fuels having anti-detonating characteristics which comprises reacting isoparafllnic hydrocarbons having less than seven carbon atoms per molecule with normally gaseous olefins having a molecular weight above ethylene in the presence of a catalyst comprising strong sulfuric acid and a low molecular weight 'mono-carboxylic acid, thereby forming products of reaction which are substantially free from products of polymerization within the gasoline boiling range.

4. In a process of forming motor fuels having anti-detonating characteristics which comprises reacting isoparafiinic hydrocarbons having less than seven carbon atoms per molecule with normally gaseous olefins having a molecular weight above ethylene in the presence of a catalyst comprising strong sulfuric acid and a low molecular weight di-carboxylic acid, thereby forming products of reaction which are substantially free from -products of polymerization within the gasoline boiling range.

5. A process of forming branched chain paraffinic hydrocarbons falling within the gasoline range, having high anti-detonating characteristics and substantially free from polymers within the gasoline boiling range, which comprises reacting isoparafllnic hydrocarbons having less than seven carbon atoms per molecule with normally ga eous olefinic hydrocarbons having more than two carbon atoms per molecule in the pres- 40 ence of strong sulfuric acid containing a low molecular weight mono-carboxylic acid whereby the polymerization of the olefins is hindered and the alkylation of the isoparafllnic hydrocarbons. by said olefins, is promoted.

6. In a process according to claim 5, wherein a relatively small percentage of the mono-carboxylic acid is employed in the catalyst.

7. In a process according to claim 5 wherein the mono-carboxylic acid is an amount less than about 15% of the catalyst employed.

8. In a process according to claim 5 wherein the mono-carboxylic acid-employed as the reaction modifying agent is glacial acetic acid.

9. A process of forming alkylated isoparafilnic hydrocarbons having high anti-detonating characteristics suitable as motor fuel which comprises commingling isoparaflinic hydrocarbons having less than seven carbon atoms per molecule with a catalyst mixture comprising strong sulfuric acid containing a low molecular weight mono-carboxylic acid, and introducing into said isoparaffin-catalyst mixture normally gaseous oleflnic hydrocarbons having more than two carbon atoms per molecule thereby alkylatlng said isoparaillnic hydrocarbons and hindering the polymerization of the olefins. 10. In a process according to claim 9 wherein the reaction modifying agent comprises a relatively small proportion of the catalyst employed.

7o 11. In a process according'to claim 9 wherein the reaction modifying agent comprises glacial acetic acid.

12. In a process according to claim 9 wherein a the reaction modifying agent comprises glacial acetic acid and wherein said glacial acetic acid liquid olefins having less than thirteen carbon comprises an amount less than 15% of the volume of the catalyst employed.

13. A process of forming alkylated isoparaifinic.

isoparaiiinic hydrocarbons and hindering the polymerization of the olefins.

14. A process for producing branched chain saturated hydrocarbons havingmolecular weights within the gasoline boiling range and substantially free from polymers within said range which comprises commingling isoparaflinic hydrocarbons of less than seven carbon atoms per molecule with a catalyst mixture containing strong sulfuric acid and a relatively small percent of a di-carboxylic acid, maintaining said mixture in a state of'agitation and at normal temperature and at a pressure sufiicient to maintain the isoparaflins in a liquid state, introducing normally atoms per molecule into 'said mixture, thereby causing a reaction between said olefins and isoparaflins to produce said branched chain saturated hydrocarbons and to hinder polymerization of the olefins and separately recovering said products of reaction.

15. A process for producing branched chain saturated hydrocarbons having molecular weight within the gasoline boiling range and substantially free from polymer within said range which comprises commingling isoparaflinic hydrocarbons of less than seven carbon atoms per molecule with a strong sulfuric acid catalyst containing relatively small proportions of glacial acetic acid, maintaining said mixture in a state of agitation and at a normal temperature and at a pressure suflicient to maintain the isoparaffins in a liquid state, and introducing normally gaseous olefins having a-molecular weight above ethylene into said mixture, thereby causing a reaction between said olefins and isoparaflins to produce said branched chain saturated hydrocarbons and to hinder polymerization of the olefins.

WILLIAM .E. BRADLEY. KARL J. KORPI. 

